In the field of X-ray capturing, the transition of X-ray capturing devices from conventional silver halide photographic devices including screens or films to CR (computed radiographic) units including photostimulable phosphor sheets has led to transition to X-ray capturing devices that capture X-ray images in the form of image signals. Various flat panel detectors (FPDs) have been developed that read electrical signals generated by a two-dimensional array of transducers, which generate electrical signals corresponding to X-ray beams irradiated from an X-ray source through a subject, as image signals. Such FPDs have been used in medical settings, e.g., hospitals, for capturing of diagnostic medical images (for example, refer to Patent Literature 1).
In X-ray capturing using an FPD, usually the FPD is irradiated once with X-ray beams from an X-ray source and passing through a subject and reads image signals corresponding to one medical image. The process of irradiating the FPD once with X-ray beams from the X-ray source and passing through the subject and capturing image signals corresponding to one medical image is referred to as general capturing. This process may also be referred to as simple capturing, which is typical X-ray capturing. Recently developed X-ray capturing devices including such FPDs further include Talbot interferometers or Talbot-Lau interferometers, which include X-ray sources for irradiation of X-ray beams onto the FPDs and a plurality of gratings (for example, refer to Patent Literatures 2 and 3). FPDs in X-ray capturing devices including Talbot or Talbot-Lau interferometers are hereinafter referred to as “X-ray detectors” in distinction from FPDs used in general capturing, but the structures of these FPDs are basically identical. X-ray capturing devices including Talbot or Talbot-Lau interferometers are hereinafter simply referred to as Talbot capturing devices.
The following Talbot capturing devices are disclosed for example. A Talbot capturing device captures multiple moire images with an X-ray detector through multiple X-ray capturing operations at variable relative positions of two one-dimensional gratings (fringe scanning), and reconstructs and generates several types of diagnostic medical images, such as X-ray absorption images, differential phase images, and small-angle scattering images, from the moire images (for example, refer to Patent Literature 4). Such method is known as Talbot method. A variation of the Talbot method described above is a Talbot-Lau method that captures multiple moire images with an X-ray detector through multiple X-ray capturing operations using a grating newly disposed near an X-ray source and moved relative to a group of other gratings, and reconstructs and generates several types of diagnostic medical images, such as differential phase images from the moire images (for example, refer to Patent Literature 5). Another capturing device includes gratings that are removable from the path of the X-ray beams irradiated from the X-ray source and is switchable between general capturing not using gratings and Talbot method (or Talbot-Lau method) using gratings (for example, refer to Patent Literature 6).
A Fourier imaging system irradiates a subject with X-ray beams once to capture one moire image through multiple two-dimensional gratings, and reconstructs and generates several types of diagnostic medical images from the moire image through Fourier transform (for example, refer to Patent Literature 7). Another type of Talbot capturing is switchable between the fringe scanning mode and Fourier transform mode through varying of the grating positions (for example, refer to Patent Literature 8).
X-ray capturing devices including Talbot or Talbot-Lau interferometers or involving Fourier transform generate moire images containing information on the subject, whereas fringe scanning generates multiple moire images through multiple X-ray irradiation operations, and Fourier transform generates one moire image for every X-ray irradiation operation. These moire images can be analyzed to reconstruct at least three types of images: an absorption image, which is similar to that obtained through normal capturing (simple capturing), a differential phase image, and a small-angle scattering image. Such images can be combined to generate a new image. X-ray capturing devices including Talbot capturing devices and X-ray capturing devices involving Fourier transform are hereinafter simply referred to as Talbot capturing devices.
It is difficult to capture an image of the cartilage portion in a joint region of a patient of interest in general capturing. Thus, for example, a large capturing device involving magnetic resonance imaging (MRI) has been used for such capturing. Such capturing involving MRI applies physical and mental stress to the patient who is the subject and causes an increase in costs. Recent research has shown that the cartilage portion in a joint region can be captured in at least a differential phase image through capturing of a dissected joint region with a Talbot capturing device (for example, refer to Non-Patent Literature 1). Research conducted by the inventors has shown that the cartilage portion in a joint region can be captured in at least a differential phase image through capturing of a non-dissected joint region of an organism with a Talbot capturing device (for details refer to Japanese Patent Application Nos. 2012-275216 and 2013-5047). Talbot capturing devices have superb functionality for capturing images of cartilage portions in joint regions, which cannot be captured through conventional general capturing; thus, Talbot capturing devices are expected to be introduced to medical facilities such as hospitals and clinics in the near future.